Cells are the fundamental structural unit of biological systems. Thus, understanding cells is essential for understanding both subcellular phenomena such as cell biology, biochemistry, and molecular biology and multicellular phenomena such as physiology. Cells may be studied using cells directly obtained from an organism or cells cultured in vitro. By analyzing cells, biologists have learned many of the complex functional relationships among biological molecules, including DNA, RNA, protein, and carbohydrate, among others, and among assemblies of such molecules. Furthermore, biologists have learned the value of using cells to understand basic cell biology principles and to screen drug candidates for treating human disease and improving human health.
Cell experiments frequently are used for pilot studies before experiments on animals or humans. For example, drug screens frequently use cells in culture to identify a small number of candidate compounds for testing in animals. Therefore, use of cells in these screens saves lives of, and reduces costs associated with, laboratory animals and allows a much larger number of experiments to be performed than would be possible in a relevant metazoan animal, such as a mammal. Furthermore, as isolation techniques and in vitro culture conditions improve for primary cells, such as embryonic and adult stem cells, an even greater number of cell analyses will be performed with cells ex vivo.
The power of cell-based test or screening systems has prompted researchers to develop a vast array of immortalized stable cell lines. Researchers have derived these stable cell lines from many different organisms, tissues, and developmental stages. A sampling of this vast array is available from American Type Culture Collection and other cell repositories. Because each cell line has distinct characteristics based on its origin, genotype, method of immortalization, culture conditions, and environmental history, no single cell line is suitable for all experiments or compound screens. In fact, because each cell line has unique properties, the biotechnology industry and basic researchers alike benefit greatly from analyzing as many cell lines as is feasible for any given experiment, compound screen, or line of research. However, the requirement for high-throughput in drug screens and other analyses with cells limits the number of different cell populations tested.
Efforts are underway to improve the speed and efficiency of cell analysis. Specifically, digitally controlled systems provide the ability to automate many aspects of cell culture, treatment, and data collection. For example, machines with robotic capabilities have been developed that plate, feed, treat, harvest, and measure properties of cells. Furthermore, automated imaging systems are capable of analyzing the properties of cell populations, single cells, and even subcellular organelles. Suitable systems are described in the following U.S. patents, which are incorporated herein by reference: U.S. Pat. No. 5,355,215, issued Oct. 11, 1994; and U.S. Pat. No. 5,989,835, issued Nov. 23, 1999.
Despite these advances, current systems still employ a brute force approach. Specifically, these systems grow, treat, and/or analyze distinct cell populations in separate containers, such as the individual wells of multi-well microtiter dishes. It is only in this way that these systems can form associations between (1) assay results obtained from the analysis, and (2) cell-identifying information, such as origin, genotype, growth condition, specific test, and/or drug treatment. Yet, this brute force approach becomes increasingly prohibitive as the number of cell types and treatments increases. For example, the analysis of 100,000 samples a day in separate sample wells, common in high-throughput screening, requires a stack of standard-sized 96-well microplates over 40 feet high each day and over 3 miles high each year, as well as the associated reagents. Thus, there is a need for more efficient systems for cell analysis.